1. Field of the Invention
The present invention relates to a magnetic recording and reproducing apparatus, and more particularly, to an apparatus which magnetically records and reproduces information on and from a recording medium by radiating light beams onto the recording medium to raise the temperature thereof.
2. Description of the Prior Art
In recent years, in the field of optical memory devices, rewritable memories have been developed, besides the read only memories such as compact disks. Among such rewritable memories, a magneto-optic disk has already been put in practical use. The magneto-optic disk employs a vertical magnetization film, such as a rare-earth transition alloy thin film, as a recording medium. For recording, as laser beams are being radiated onto the recording medium, an external magnetic field is applied to the irradiated recording medium. For reproduction, the Kerr effect is utilized in which, when laser beams are radiated onto the recording medium, the plane of polarization of the reflecting beams rotates in different directions depending on the existence of data on the recording medium.
A recording and reproducing method which employs a ferromagnet such as CrO.sub.2 for a recording medium has been proposed. (See Nomura, Yokoyama, "Proposed Magneto-Optic Video Recording Systems Using Thermoremanent Techniques, NHK Technical Research Laboratories, 1979, Institute of Electronics and Communication Engineers of Japan Technical Research Report MR79-3.) In this method, recording is performed by applying an external magnetic field to the recording medium of which coercive force has been reduced by radiating laser beams thereto, by means of a magnetic head for recording, as is done in the case of the above magneto-optic disk, and reproduction is magnetically performed by using a magnetic head for reproduction.
However, in the above optically assisted magnetic recording and reproducing method, it is difficult to have a magnetic head for reproduction that has a sufficiently small width to meet the width of a track of the recording medium. This results in reproducing unnecessary signals on the tracks on both sides of a track from which reproduction is intended, thereby causing the problem of crosstalk.
Such crosstalk may be prevented if the track width is made larger than the width of the magnetic head for reproduction. In this case, however, the track width must be significantly large, and thus the recording density disadvantageously decreases.